It is well known to those skilled in the art that gelled or crosslinked water-soluble polymers are useful in enhanced oil recovery operations. They have been used to alter the permeability of underground formations in order to enhance the effectiveness of water flooding operations. Polymers along with an appropriate crosslinking system are injected in an aqueous solution into the formation. The polymers then permeate into and gel in the regions having the highest water permeability. A conventional crosslinking system consists of phenol and formaldehyde. Any fluids injected into the formation in subsequent water flooding operations, will then be diverted away from the regions in which the gel formed to areas containing unswept oil.
Although this technique is effective in enhancing hydrocarbon production, it does have problems. One of the primary problems facing the use of conventional crosslinking system is that formaldehyde is carcinogenic and is not environmentally acceptable.
It would therefore be a valuable contribution to the art to develop an organic crosslinking system which is more environmentally acceptable and forms comparable or better gels, compared with the phenol-formaldehyde crosslinking system, for oil field operations.